Looking at Doc/tutorial/classes, the section "Python Scopes and Namespaces" is full of heavy/deep information. I expect that people who would be able to properly digest that info are people who are already advanced at Python, and therefore maybe it should be moved to some cookbook (or language reference). I would prefer something gentler, since the tutorial is for Python newbies who aren't necessarily conversant with OO concepts.
There can of course be links to heavier material for deeper understanding.